1. Field of the Invention
The present invention relates to a recording device of the type using continuous paper and a method of automatically feeding continuous paper. More particularly, the present invention is concerned with a recording device capable of automatically setting continuous paper at a recordable position when the paper is mounted to the device, and a method of feeding continuous paper and automatically setting it in a recordable position.
2. Description of the Prior Art
A thermal printer belonging to a family of recording devices of the type described includes a platen roller and a thermal head facing each other at a recording section. The thermal head has a plurality of heating elements arranged thereon. While continuous paper paid out from a roll is passed through a nip between the platen roller and the thermal head, a current is selectively fed to the heating elements of the head in accordance with an image signal. As a result, an image represented by the image signal is printed on the paper. The prerequisite with this kind of printer is that serial numbers, dates and other information be accurately printed on preselected positions of, e.g., admission tickets sequentially formatted on the continuous paper. To meet this requisite, the thermal printer needs a mechanism for detecting the leading edge of the paper in order to position the paper and then automatically feeding the paper.
FIG. 7 shows a specific configuration of a thermal printer having the above mechanism and taught in Japanese Patent Laid-Open Publication No. 2-293251published on Dec. 24, 1991. As shown, the printer includes a roll supporting section 11 supporting a roll of continuous paper 10. Both the roll and the paper constituting it will be designated by she same reference numeral 10 hereinafter. A recording section 12 prints an image on the paper 10 paid out from the roll 10. A cutting section 30 cuts off the paper 10 at a preselected length after the printing of the image. An outlet roller pair 18 drives the cut length of the paper, or sheet, out of the printer. The recording section 12 has a platen roller 13 and a thermal head 22 facing and contacting each other. The cutting section 30 has two cutting edges 29 and 31 facing each other. The outlet roller pair 18 is made up of rollers 17 and 19 facing each other.
A pair of drive rollers 15 are mounted on the roll supporting section 11 in the vicinity of the bottom of the section 11. The drive rollers 15 support the roll 10 and cause it to rotate. A sensor 16, a guide 20 and a sensor 14 are arranged between the roll supporting section 11 and the recording section 12. The sensor 16 is responsive to the leading edge 10a of the paper 10. The guide 20 is movable toward and away from the periphery of the roll 10. The sensor 14 is responsive to the passage of the leading edge 10a of the paper 10. Guide plates 21 and 23 facing each other are positioned between the recording section 12 and the cutting section 30 while guide plates 25 and 27 facing each other are positioned between the cutting section 30 and the outlet roller pair 18.
When the roll 10 is new, it has a mark indicative of the leading edge of the paper 10 printed on the leading edge. When the new roll 10 is rotated counter clockwise, as viewed in FIG. 7, by the drive rollers 15, the sensor 16 senses the above mark of the paper 10. Then, the guide 20 is moved toward the periphery of the roll 10. As a result, the leading edge 10a of the paper 10 is separated from the periphery of the roll 10 by the edge of the guide 20.
While the roll 10 is in rotation, the leading edge 10a of the paper 10 is conveyed to the nip between the head 22 and the platen roller 13. When the sensor 14 determines that the leading edge 10a of the paper 10 has moved away from the sensor 14, the platen roller 13 and outlet roller pair 18 are caused to start rotating while the guide 20 is retracted to its initial position. While the paper 10 is sequentially passed through the nip between the head 22 and the platen roller 13, the head 22 prints an image on the paper 10, as stated earlier. Subsequently, the paper 10 is conveyed to the outlet roller pair 18 via the guides 21 and 23, cutting section 30, and guides 25 and 27. When the paper 10 is driven out by the outlet roller pair 18 by a preselected length, the cutting section 30 cuts off the paper 10.
The problem with the above conventional printer is that it cannot detect the leading edge 10a of the paper 10 unless the mark indicative of the leading edge 10a exists on the roll 10, e.g., when the roll 10 whose leading edge 10a has been cut away during the past recording operation is again mounted to the printer. The printer therefore cannot automatically set such a roll 10 lacking the mark.
To solve the above problem, the leading edge of continuous paper may be detected by an optical implementation, as proposed in the past. An optical implementation, however, is not practicable without resorting to a highly accurate optical sensor. Moreover, should the continuous paper be of the kind including perforations, grooves or folds, the optical sensor would sense them as leading edges and would prevent desired information from being printed at expected positions.